Flexo printing used for printing a packaging material such as cardboard, paper container, paper bag, or film for flexible packaging, wall paper, construction interior material such as wall paper or decorative plate, or label particularly raises its ratio among various printing methods in recent years.
A printing form plate used for the flexo printing frequently uses a photosensitive resin in general. The photosensitive resin includes a liquid-state resin and solid-state resin form plate formed like a sheet. A photosensitive-resin relief printing form plate on which a relief image is formed through a negative film is obtained by using a process unit dedicated to liquid-state or solid-state form plate and printing is performed by directly attaching the relief printing form plate to a plate cylinder of a printing machine or once attaching the relief printing form plate to a carrier sheet or sleeve for printing and setting the carrier sheet or sleeve for printing to the plate cylinder.
Moreover, for a photosensitive solid-state form plate, a formation (referred to as flexo CTP form plate) (Patent Document 1) for performing exposure through a mask image after forming the mask image by laser drawing by setting a thin removable infrared photosensitive layer (black layer) formed by an infrared laser beam on the photosensitive resin surface instead of using a negative film correspondingly to progress of a recent digital image technique and an external-surface-drum-type drawing apparatus (Patent Document 2) for forming a mask by selectively removing an infrared photosensitive layer of a flexo CTP form plate by an infrared laser beam in accordance with digital image information are disclosed.
In the case of the flexo CTP form plate, relief exposure is performed through the above infrared photosensitive layer mask and exposed photosensitive resin is optically cured. Thereafter, a relief image is formed by washing out unexposed resin by perchloroethylene (1,1,1-trichloroethylene) alone or combining it with alcohol such as n-butanol or carbon-hydride solvent developer such as sorbit (trade mark: produced by McDiarmid) which is a non-chlorine substitute solvent and passes through a drying step and finishing step (photochemical treatment and chemical treatment) to obtain a flexo printing form plate. When winding even this flexo CTP form plate on a plate cylinder, a slight gap is left between the front end and the rear end of the CTP form plate similarly to the case of a normal form plate. Therefore, the flexo CTP form plate is unsuitable for seamless printing.
Therefore, printing of a conventional seamless endless pattern has depended on printing by a gravure form plate or printing by a relief in which an image is formed on a vulcanized rubber roller by manual carving.
In the case of plate making of a gravure form plate, a series of complex steps such as application of a developer to a copper cylinder, exposure, etching, film removal, and chromium plating is performed by using a lot of time. Therefore, the plate making cost is very high. Moreover, to adjust a cell depth, very delicate control is requested for an etching condition. Therefore, operations such as etching and plating are used in a plate making step in addition to an operation depending on the perception of an expert. Therefore, the operations may become a generation source of waste water pollution.
Furthermore, the rubber roller relief by manual carving described above has critical defects that a high level of skill is requested for the plate making technique, a fine design cannot be made because of manual carving, and it is impossible to reproduce a half tone dot.
However, the vulcanized rubber can be used together with a solvent having a strong corrosion characteristic and has a preferable ink transfer characteristic, high elasticity, and high compressibility. Recently, it is possible to obtain a relief printing form plate by directly carving a rubber roller by an infrared laser beam in accordance with a digital image signal instead of manual carving because a digital image processing technique and laser carving technique are advanced.
Commercially-used rubber includes natural rubber and synthetic rubber. As an example of synthetic rubber, there is ethylene-propylene-diene-monomer-elastomer (EPDM). It is possible to provide a flexo printing form plate material which can be carved by a laser beam by using the EPDM. A flexo printing form plate material manufactured from natural rubber or synthetic rubber requires vulcanization by sulfur, sulfur-contained compound, or peroxide in order to perform bridging. Moreover, after the flexo printing form plate material is thus vulcanized, the material requires polishing in order to obtain a uniform thickness and smooth surface suitable for printing. This requires an extreme lot of time and the operability is bad.
Therefore, to solve the above problems, many methods and apparatuses for manufacturing a lot of relief materials for seamless printing to which a photosensitive polymer (liquid-state or sheet-like solid-state resin form plate) widely used in the relief printing field and advantageous for a manufacturing method is applied are proposed.
As a method for setting a printing form plate on a sleeve, a method (Patent Document 3) is known which manufactures a form plate material on which a seamless continuous printing pattern using liquid-state photosensitive resin diluted by a solvent. Patent Document 3 discloses a manufacturing method for rotating an endless raw material, supplying liquid-state photosensitive resin to the rotating surface and smoothing the resin by a doctor.
Moreover, Patent Document 4 discloses a spraying, dipping, and applying roller method or an extruding machine method.
Furthermore, many seamless printing relief manufacturing methods and apparatuses respectively using a photosensitive resin solid-state form plate instead of a liquid-state photosensitive resin are disclosed.
For example, Patent Document 5 discloses a manufacturing method for superimposing a plurality of thermoplastic photosensitive films and winding them on a cylinder, bringing an integrated photosensitive film obtained through pressurizing and heating into accurate dimensions, and then applying the shaping treatment to the film by mechanical compression, grinding, or polishing, and calendar-finishing the film.
Moreover, Patent Document 6 discloses a method and an apparatus for manufacturing a seamless sleeve through rolling and glazing in accordance with a calendar roller method by heating and melting thermoplastic photosensitive resin on the outer periphery of a sleeve supported by a mandrel.
Furthermore, a method for manufacturing a form plate material on which a seamless continuous printing pattern using liquid-state photosensitive resin can be printed is known by the application of the present applicant (Patent Document 7).
In the case of the Patent Document 7, an original form plate for seamless printing is manufactured in accordance with an applying step of supplying liquid-state photosensitive resin to the outer periphery of a cylinder while rotating the cylinder and an exposing step of applying active rays to the applied liquid-state resin layer and forming a resin cured layer. Thereafter, manufacturing method and apparatus for forming a relief image on a resin cured layer of the original form plate for seamless printing by laser carving in accordance with a digital recording signal are disclosed.
Patent Document 8 relates to a blanket for offset printing and discloses a configuration and a structure capable of performing a corresponding step by linearly moving a base sleeve while rotating the base sleeve though a technical field different from the present invention and thereby using individual mechanism set to a fixed position.
That is, manufacturing apparatus and method are disclosed which cut a base sleeve at a desired length by first applying a radioactive polymer by a liquid applicator, smooth the resin liquid surface by an optional surface finisher, then form a polymer cured layer through radiation (preferably, ultraviolet light) exposure, use any one of a scraper, planer, and polisher and thereby smooth the polymer cured layer.
As a liquid applicator, a blade, roller, nozzle, spray, and anilox roll are listed which are generally-used publicly-known techniques and a surface finisher only lists a doctor blade, scraper, planning machine, and polisher which are also general publicly-known techniques. Therefore, portions in which the invention of Patent Document 8 seems to have novelty compared to an preceding invention or conventional publicly-known technique are the following two points (1) and (2).
(1) Continuous treatment is performed by rotating and linearly moving a base sleeve by setting a treatment mechanism to a fixed position.
(2) A mechanism for cutting a base sleeve at a desired length is included.
In the case of the embodiment of the Patent Document 8, the following steps are illustrated: a step of rotating and linearly moving a base sleeve, a step of applying a radioactive curing polymer to the base sleeve in a spiral mode by a spray mechanism, ten smoothing the base sleeve by a first-stage circular smoothing station, a step of forming a polymer cured layer through the exposure by an ultraviolet light source, a step of smoothing the polymer cured layer at a second-stage circular smoothing station same as the first stage, and a step of forming a second polymer layer on the polymer cured layer by a second spray mechanism.
Details of steps after the second poly layer are unknown because a corresponding mechanism is not illustrated. However, judging from the context of this embodiment, a method and an apparatus are illustrated which are estimated as the fact that a first-stage smoothing step, an ultraviolet exposing step, and second smoothing step are continued similarly to the case of the first polymer layer.
Patent Document 1: JP11-153865A
Patent Document 2: JP8-300600A
Patent Document 3: JP52-62503A
Patent Document 4: West Germany Patent Application Laid-Open No. 2640105 (Specification)
Patent Document 5: JP63-202751A
Patent Document 6: Japan Patent No. 3209928
Patent Document 7: JP2002-079645A
Patent Document 8: JP2003-29848A
However, there are the following problems in the above-described conventional method and apparatus for manufacturing a relief material for seamless printing.
To obtain a seamless relief printing form plate material from a photosensitive resin solid-state form plate, grinding and polishing for uniforming a form plate thickness and smoothing surface are generally performed similarly to the case of the above rubber after winding a photosensitive resin solid-stage form plate on the surface of a cylinder as shown in the above Patent Documents 5 and 6, pressurizing, heating, and fusion-bonding the matching joint of an edge by a calendar roller or the like and thereafter a grinding or polishing step for uniforming a form plate thickness and smoothing surface are performed similarly to the case of the above rubber. Moreover, a uniform carbon black layer having no pin hole on the surface as shown in the above Patent Document 1 is formed as a substitute for a negative film, selectively ablation-removed by a digital-controlled laser-drawing apparatus as shown in the above Patent Document 2 to manufacture a mask and a seamless relief printing form plate is obtained by passing through a publicly-known exposure, solvent-phenomenon, drying, and post-exposure steps.
However, as pointed out in the above description, it is difficult to say that seams are completely absent and discontinuity of a printed matter at a seam frequently becomes a problem.
In the above Patent Documents 3 and 4, photosensitive resin is not practically used due to problems of odor and pollution because of diluting the resin by a solvent before it is applied and evaporating it after it is applied to cure a photosensitive resin layer, a problem of reproduction by expansion of an image caused by imperfect adhesion between a negative film and a photosensitive resin layer because of simply pressure-welding the negative film without using vacuum attraction, a problem of involvement of bubbles which is the fate of liquid-state resin, or a problem of liquid-state resin molding that the total accuracy as a seamless printing form plate is not kept in a practical use area.
In the above Patent Document 7, a resin supply mechanism (bucket) is closed and supply of liquid-state photosensitive resin to a cylinder is stopped, the liquid-state resin held by the doctor blade side is transferred to a part of the liquid-state resin layer whose applied thickness is already uniformed at the moment when the doctor blade at the front end of the bucket is separated from the resin applied to the outer periphery of the cylinder and becomes an irregular thickness or a defect of a convex portion and smoothness is lost. Therefore, the accuracy of a printing form plate is out of a printing applying range to cause a printing trouble. Moreover, the following problems are included for practical use: a problem of involving bubbles when the bucket is opened or closed or in the smoothing step by the doctor blade and a deficit portion is formed nearby the resin layer surface and a problem that a resin applied width is fixed because of the bucket structure and it is impossible to easily correspond to a size change of a cylinder width.
In the above Patent Document 8, when applying liquid to a rotating cylindrical object at a uniform thickness, the liquid is easily flown due to gravity or rotational centrifugal force unless the liquid has a viscosity to a certain extent and the shape of the liquid is not easily held. Because the thickness of a resin layer of a relief printing form plate ranges between 0.5 and 7.5 mm (between 1.14 and 2.84 mm for laser carving), the layer cannot be applied at a uniform thickness and there is a hazard that the liquid is separated from the cylindrical object and dripped. The hazard that the liquid is dripped most frequently occurs when the applied liquid reaches the lowest position.
Moreover, When directly using the liquid-state photosensitive resin used in accordance with the planar exposure method of the flexo-printing relief plate making system for laser carving, a lot of foreign matter (including viscous liquid) is produced on a resin cured layer to be laser carved. Therefore, occurrence of the foreign matter is restrained by adding an inorganic porous material. However, it is a current situation that the viscosity of the liquid-state photosensitive resin is extremely increased by adding the inorganic porous material.
Thus, the liquid-state photosensitive resin for relief printing having a high laser carving characteristic is very viscous compared to a general liquid-state photosensitive resin. When applying the high-viscous liquid-state resin by a spray mechanism in a spiral mode, there is a problem that bubbles are generated on the boundary between the resin applied through the previous rotation and the newly applied resin. Moreover, a specific embodiment showing that by what means it possible to spray-apply the high-viscous liquid-state photosensitive resin is not described.
Moreover, at the first-stage smoothing station, extra liquid-state resin is diffused from the both ends of the station contact face to the circumference when the applied liquid-state resin passes through the narrow area of the station. Therefore, it affects the liquid-state resin smoothed by the previous rotation and rather causes the thickness of the applied liquid-state resin to deteriorate than smoothing.
Moreover, a problem of involving bubbles when the front end of the applied liquid-state resin contacts with the above station is included. Therefore, it is possible to estimate that practical use is not realized. Furthermore, about exposure, there is no specific description that a resin layer optically-cured by a high-intensity ultraviolet light contributes to improvement of printing reasonableness as relief printing. Thus, liquid-state photosensitive resin to be used is different depending on purposes of a laser-carving seamless printing original form plate and an offset printing blanket, it is clear that manufacturing method and apparatus are different.
The present invention is made to solve the problems and its object is to provide a method and an apparatus for manufacturing a relief material for seamless printing capable of manufacturing a relief material for seamless printing having a high-accuracy thickness and high printing reasonableness by preferable surface smoothing characteristic and completely free from seams, improving the operability by making conventional negative-film manufacturing step and solution developer step unnecessary, and realizing resource saving and environment maintenance.